Automatic compressor control system



Dec l, 1931.

J. W. SANFORD AUTOMATIC COMPRESSOR CONTROLSYSTEM 2 Sheets-Sheet 1 FiledAug. 10, 1928 Imeni'ow: JWm Z0. :Sanfbmi.

m -Mm- J. W. SANFORD AUTOMATIC comrnssson CONTROL SYSTEM Filed Aug. 10.1928 2 Sheets-Sheet 2 J 6 & wmw

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Patented Dec. 1; 1931 UNITED STATES PATENT OFFICE JOHN W.8ANI'ORD, OIWONT, m nmsnmn, ABSIGNOB TO sunuvan' IA- GHINERY COMPANY, A CORPORATIONOF K.AS8AOHUBETTB AUTOILLTIO OOHPBEBSOB common Application filed August10, 1928. Serial No. 298,701.

My invention relates to automatic compressor control systems.

When compressors are driven by electric motors, it becomes important toreduce the 3 cost of power to a minimum. The rate char ed by powercompanies is frequently base on the maximum load demand over a certaininterval of time, usually three or four minutes or more. With theunloading 10 mechanism heretofore provided for automaticall loading andunloading the comressor 111 response to variations in demand orcompressed fluid the compressor and its driving motor are made to rununder full load when the pressure is low and this fully loaded intervalmay be longer than the interval fixed by the power company as its basisfor rates. It is also a fact in many installations that seldom if everis the full 90 demand placed on the compressor and a common occurrenceis a compressor installation of one or more compressors whose capacityis around two hundred percent of the average demand. In this instance,if the com-' pressor is provided with an unloader which will permit fullload to be placed on the compressor for a period longer than the maximumdemand interval fixed by the power company, it will be seen that theuser of compressed air may be forced to pay almost twice the amount forpower that would be necessary if the load could be properly distributed.At times, as is frequently the case in compressor installations formines, the demand for air may be even considerably lower than fiftypercent of the capacity of the compressor, but if the compressor and itsmotor are forced to run' under full load over any considerable length oftime the cost of power will be practically as great as it would be ifthe demand for air were around one hundred percent load.

It is therefore the primary object of my invention to provide compressorcontrolling mechanism which will meet the above conditions andenable theload on the compressor to be controlled so as to keep the cost of powerdown to a minimum consistent with the demand for air. Another object isto provide improved means for, controlling the load on a motor so thatthe load will not exceed a certain predetermined percentage of fullload. A further object is to provide improved means for controlling theload on a compressor so that the average load placed on its drivingmotor over a certain predetermined small interval of time will notexceed a certain percentage of full load. Still another object is toprovide improved means for varying the maximum avera e load on acompressor over a certain pre etermined time interval and to providemeans for regulating said time interval. Other objects and advantages ofmy invention will hereinafter more full appear.

In the accompanying drawings I have shown for purposes of illustrationone form which my invention may assume in practice.

In these drawings,- I Fig. 1 is a diagrammatic view in elevation of acompressor system with my improved control mechanism associatedtherewith.

Fig. 2 is also a diagrammatic view illustrating the various elements ofthe fluid pressure controlled unloader.

Fig. 3 is a detail sectional view through one of the valves which may beemployed in my controlling system.

Fig. 4 is a vertical sectional view through the timing elements of myimproved control mechanism.

Fig. 5 is an end elevation of the mechanism illustrated "in Fig. 4:.

Figs. 6 and 7 are elevation views of the timing mechanism, showing theparts in different positions.

In carrying out my invention I preferably employthe usual elements of anunloading device of the pilot valve controlled ty e wherein the unloaderis moved to unloa ing position when placed under pressure throughoperation of the pilot valve. In the line leading from the pilot valveto the unloader in one embodiment of my invention I inters pose aspecial double throw automatic threeway valve from which also leads aconnection to the receiver tank independent of the pilot valve. In thislatter connection is installed a three-way valve which is capable ofpermitting air to flow from the receiver tank to the first three-wayvalve or to cut ofi the receiver tank and vent the line leading to saidfirst three-way valve. The operation of this latter valve is controlledby a special timing mechanism which may assume an almost unlimitednumber of concrete forms. The operation of the special double throwthree-way valve is such that the timing mechanism may put the unloaderunder pressure independently of the action of the pilot valve and alsopermit the pilot valve to control pressure to the unloader when thetlming mechanism is in position to perm1t loadaeferring to the specificembodiment of my invention illustrated in the drawings, there is shownin Fig. 1 a compressor of the angle compound type having a low pressurecylinder 1 and a high pressure cylinder 2 wlth an intercooler 3interposed between the two cylinders' Compressed fluid is dischargedfrom the high pressure cylinder through a line 4 to a usual receivertank 5. Since the specific construction of the compressor dr ving motordoes not enter into the present invention, it has not been shown indetail, but a direct connected motor is indicated at 6. The unloaderillustrated is of the total closure intake type having a casin 7 towhich fluid is supplied directly from tie atmosphere or through asuitable pipe 8. Low pressure fluid is supplied from this casing to thecompressor throu h a connection 9 under the control of a ouble seatvalve 10 which is actuated through a stem 11 and piston 12. The valve isnormally held in its u per or loaded position by a spring 13 there ypermitting fluid to flow freely to the intake of the compressor. Thisunloader valve is actuated to closed or unloaded position by fluidpressure acting in the cylinder 14 and the amount of movement iscontrolled by an adjust-able stop 15. For the purpose of controllingpressure in the unloader cylinder 14, my improved control systemincludes a usual pilot valve mechanismgenerally indicated 16 which maybe of any of the well known types, the one illustrated herein being ofthe type known as the Penn pilot valve. This 1pilot valve mechanismoperates in a well nown manner in response to a predetermined highreceiver tank pressure to establish a connection between the receivertank 5 and the unloader cylinder by way of a line 17 leading from thereceiver tank through a three-Way valve mechanism 18 to the line 19 andthence to the unloader cylinderthrough a connection 20 under the controlof a special threewway. valve generally designated 21.

When the pressure in the receiver tank reaches a predetermined minimum,the pilot valve mechanism 16 operates the three-way valve 18 to closethe line from the receiver tank and vent the line leading from theunloader cylinder. Leading to the special threeway valve 21 is a thirdconnection 22 which leads to the receiver tank 5 through a threewayvalve 23 and a pi 24.

The construction 0 the s ecial three-wag valve 21 will now be brie ydescribed. valve element 25 is reciprocably mounted in a cylinder 26 andhas conical end portions 27 and 28 which are adapted to close againstcooperating seats in the opposite ends of the valve casing to controlcommunication between lines 19 and 22 and the interior of the valvecasing. The opposite end flanges 29 and 30 are provided with suitablenotches 31 and 32 for establishing free communication between either oflines 19 and 22 and the unloader cylinder through the interior of thevalve casing. It will of course be understood that any type of valve maybe used in this connectlon which will operate in a manner substantiallysimilar to the operation of the present valve.

The three-way valve 23 is herein illustrated as being of the same typeas that indicated at 18 employed on the Penn pilot valve. Theconstruction of this valve is shown in section in Fig. 3. The valveelements 33 and 34 have conical portions cooperating with conical seats35 and 36 in the valve casing and are provided with oppositely directedabutting stems 3,7 and 38. A spring 39 normally tends to hold the valvesin their lower position, thus closing valve 34 and opening vent valve33. Fluid flows freely throu h the valve casing around the valve stems 3or 38 to or from the connection 40 which communicates with pipe 22. Thevalve elements are controlled by means of a movable plunger 41 which isresiliently connected through a spring 42 to the lower valve 33. Asshown in Fig. 5, the three-way valve 23 ismounted on a box-like casing43 by means of a suitable bracket 44. The plunger 41 extends downwardlyinto contact with a cam member 45 which is pivotally mounted on abracket 46 fixed to casing 43.

The timing mechanism for controlling the movements of cam member 45 isdriven from a gear 47 on the main shaft 48 of the compressor through anysuitable gear reduction mechanism including a gear 49. A shaft 50 isos-' cillated by thefgear 49 through any suitable means such as a link51 and a crank 52.

A pawl carrying member 53 is keyed to the shaft 50 and oscillatedthereby. The pawl 54 is pivoted to the member 53 at 55 and engages teethon a ratchet wheel 56. The ratchet wheel is thus intermittently rotatedin one direction, being held against rotation in the opposite directionby a pawl 57 mounted on a stationary pivot 58. Y The ratchet wheel 56 isfixed to a hollow shaft 59 which surrounds shaft 50 and rotates in abearing 60. Suitable means are provided for varying the number of teethover which the pawl 54 may move at each oscillation of the pawl carryingmember. This means herein comprises a shield 61 which is fixed to an arm62 rotatably mounted on the shaft 50. In order to adjust theposition ofthis shield, a hand wheel 63 carries a nut which coo erates with a screw64 to raise and lower a shdingblock 65 which in turn is connected to thearm 62 by means of a link 66. The screw and sliding block are mounted ina suitable guiding member 67 mounted on the box-shaped member 43. On

' the end of the hollow shaft 59 is mounted a plate 68 which carries afixed pin 69 projecting laterally therefrom and which has a series ofholes 70 formed therein. It will be noted that these holes are arrangedin a circle about the center of the plate and are adapted to receive aremovable pin 71. It will be noted that-the pin 69 is rotated so as tostrike the arm 72 of the cam member 45 while pin 71 is positioned so asto strike the arm 73 of this cam member.

It is believed that the operation of my improved controlling mechanismwill be readily understood in view of the above description.

' Assuming first that the parts are in the pomain in its upper positioneven through the pilot valve 16 operates to put pressure through line 19since the area subjected to llve pressure on the lower end of the valveis materially greater than the area subjected to pressure at the upperend of the valve. It will be noted that in Fig. 6 the pin 69 has justoperated on the arm 72 to move the cam 45 into a position to elevate theplunger 41 and thus hold the valve elements 33 and 34 in their upperposition as shown in Fig. 3. If

it is desired to prevent the compressor from carrying more than acertain percentage of full load, the pin 71 will be displaced angularlycounterclockwise relative to the pin 69 an amount corresponding to thepercentage of desired unloading. As shown herein, the pin 71 is placedin the first hole or in position allowing the compressor to be loadedabout ninety percent of the time. When the timing mechanism thusoperates to elevate the plunger 41, thecompressor is unloaded even ifthe pilot valve 16 is in loaded position. For example, if the pilotvalve is in position to load the compressor, the line 19 will be ventedto atmosphere and when the plunger 41 is elevated by the timingmechanism, pressure is admitted through line 22 and acts on the lowerend of the valve, thereby elevating the same and admitting pressure tothe unloader cylinder.

Operation of the compressor will actuate the timing mechanism throughthe reduction gearing 47, 49 and the plate 68 will be rotated in aclockwise direction by means of the ratchet and pawl mechanism 54, 56.The speed of rotation of this'plate may be varied by changing theposition of the shield 61 so that the pawl 54 may catch any number ofteeth from one to seven or eight if desired. Upon rotation of the plate68, the pin 71 engages arm 73 of the cam member and oscillates the camto the position shown in Fig. 7, allowing the plunger 41 to drop. Thelower end of the cylinder 26 is thus vented to the atmosphere throughthe line 22 and valve 23. The valve 25 therefore drops and permits theunloader pilot 16 to control loading and unloading in the usual mannerduring the period of operation between the time when pin 71 leaves thecam member and pin 69 again engages the cam member. If it is assumedthat both the pilot valve 16 and the timing mechanism are in positionsto t pressure on both sides of the three-way va vs 21, the valve will beheld in the position where it was at the time the condition wasinitiated due to the fact that one or the other of conical ends 27 or 28will be covered by engagement with its respective seat, and hence therewill be an unbalanced pressure force-acting on the valve at the openedend thereof. It will thus be seen that the valve is prevented from beingheld in a position midway between its two extreme positions and willthus permi unloading of the compressor.

As a result of my inventiomit will be evident that means are providedfor limiting the load which may be placed on the compressor. Also theinterval during which it is desired that the average load shall bemaintained at a minimum may be varied to suit difi'erent conditions byvarying the speed of rotation of the plate 68. This is accomplished byadjusting the position of the shield 61 by means of hand wheel 63.Besides varying the length of the total interval, the proportion ofunloaded to loaded operation may be varied by selecting the proper hole70 to receive the removable pin 71. Also, if it is desired to permit thecompressor to run loaded without interference from the timing mechanism,this ma be accomplished either by removing the pm 71 or disengaging thepawl 54 from the ratchet wheel. The cost of power is thus kept at aminimum consistent with the average demand for air by adjusting theposition of pin 71 to the proper percentage of full load. While thiscontrol mechanism will allow the compressor to run fully loaded for ashort period of time, the average load over a period designated by thepower company will be reduced to a minimum.

While I have in this application specifically described one form whichmy invention may assume in practice, it will be understood that thisform of the same is shown for purposes of illustration and that the,invention may be modified and embodied in various other forms withoutdeparting from its spirit or the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent is:

1. In an automatic compressor control system, a compressor, an unloadingdevice for unloading said compressor when subjected to pressure, a pilotvalve for controlling said unloading device to load and unload thecompressor in response to receiver tank pressure, and means forpreventing said pilot valve from relieving said device of pressure overa predetermined percentage of time.

2. In an automatic compressor control system, a compressor, an unloadingdevice for unloading said compressor when subjected to pressure and forloading the same when relieved of pressure, a pilot valve forcontrolling pressure to said unloader to load and unload the compressorin response to receiver tank pressure, a three-way valve in the lineleading from the said pilot valve to said unloader, a second connectionleading from said three-Way valve to the receiver tank, and means forpreventing said pilot valve from relieving the pressure of said unloaderat predetermined time intervals including means for conducting pressurefluid through said second connect-ion and through a valve to saidunloader.

3. In an automatic compressor control system, a compressor, an unloadingdevice for unloading said compressor when subjected to pressure, a pilotvalve for controlling pressure to said unloader to load and unload saidcompressor in response to receiver tank pressure, a three-way valve inthe line leading from said pilot valve to said unloader, a secondconnection leading from the three-way valve to the receiver tank, andmeans for preventing said pilot valve from relieving said unloader ofpressure at intervals including means for controlling said secondconnection for intermittently allowing pressure fluid to flow from saidreceiver tank through said three-way valve to the unloader, saidcontrolling means including means for venting the unloader through saidthree-way valve, and means in said three-way valve for preventingcommunication between the unloader and that one of the other connectionswhich is not subjected to pressure.

4. In an automatic compressor control system. the mechanism set forth inclaim 3 including means provided by said three way valve for holding thesame in one of its extreme positions when both the connections from saidpilot valve and the other connection from the receiver are subjected topressure.

5. In combination, a power consuming determined period atdefiniteregular time intervals, said mechanism being adjustable to varythe duration of said intervals while maintaining said periods uniform.

6. In combination, a power consuming device, means for limiting themaximum average power required by said device over a definite period oftime to a predetermined .percentage of full load, said means comprisingmechanism to reduce the load after uniform periods of loaded operation,said mechanism being adjustable to vary the periods of reduced loadwhile maintaining the periods of loaded operation of uniform length.

7. In combination, a power consuming device, means for limiting themaximum average power required by said device over a definite period oftime to a predetermined percentage of full load, said means comprisingmechanism to reduce the load for a predetermined time at definiteregular time intervals, said mechanism being adjustable to vary thefraction of each interval when the mechanism is effective to reducetheload and also to vary the frequency of said intervals.

8. In an automatic. compressor control system, a compressor, anunloading device for unloading said compressor when subjected topressure, a pilot valve to supply pressure fluid to said unloader tounload the compressor in response to high compressor discharge pressureand to vent said unloader to cause loading of the compressor upon theoccurrence of low compressor discharge pressure, and means operating atpredetermined time intervals for supplying pressure to said unloadingdevice and preventing the effective venting of the same by said pilotvalve regardless of compressor discharge pressure.

9. In combination, a fluid compressor, and means for limiting themaximum average power required by said compressor over a definite periodof time to a predetermined percentage of full load, said meanscomprising mechanism for eflecting total unloading of the compressor,timing mechanism driven from said compressor, and means actuated by saidtiming mechanism to cause unloading for a predetermined time at definiteregular time intervals, said timing mechanism being adjustable to varythe frequency of said intervals.

10. An automatic compressor control system comprising, in combination. acompressor, means for automatically loading and unloading saidcompressor in response to variations in compressor discharge pressure,au-

tomatic means for effecting unloading of said compressor independentlyof variations in compressor dlscharge pressure, and means associatedwith both of said automatic means for preventing under certainpredetermined conditions efiective operation of one of said automaticmeans.

11. An automatic compressor control system comprising, in combination, acompressor, means for automatically 'loading and unloading saidcompressor in accordance with variations in compressor dischargepressure, and automatic means for effecting unloading of said compressorindependently of variations in compressor dicharge pressure including avent and means for automatical- 'ly variably controlling the same inaccordance with desired operating conditions.

12. An automatic compressor control system comprising, in combination, acompressor, fluid actuated means for automatically loading and unloadingsaid compressor in accordance with variations in the compressordischarge pressure, and automatic means for effecting unloading of saidcompressor independently of variations in compressor discharge pressureand while the compressor runs at normal speed, including a vent for thefluid pressure which actuates said loading and unloading means, andmeans for controlling said vent automatically upon actuation of one ofsaid automatic load controlling means.

13. In combination, a power consuming device, means for limiting themaximum average power required by said device over a given period oftime to a predetermined percentage of that at full load, said meansincluding a fluid controlled mechanism for affecting the load on saidpower consuming device, and a fluid actuated control valve forcontrolling said load mechanism to efi'ect said limited maximum averagepower.

14. In combination, a power consuming device, means for limiting themaximum average power required by said device over a definite period oftime to a predetermined percentage of that at full load, said meansincluding a fluid controlled mechanism for effecting loading orunloading of said power consumlng device, a fluid actuated control valvefor controlling said loading and unloading mechanism, a vent for theactuating fluid of said controlled mechanism and control valve, andmeans adapted to variably control said vent automatically duringoperation of said loading and unloading mechanism.

reducing mechanisms and adapted to have a plurality of operatingpositions in either of which the controlling member is immovable, saidcommon member being in one position to effect load reduction by one ofsaid mechanisms and in another position to eflect load reduction by theother of said mechanisms.

16. In combination, a power consuming device, means for limiting themaximum average power required by said device over a given period oftime to a certain percentage of that at full load, said means comprisingmechanism to reduce the load on said device, additional means forefi'ecting reduction of the load on said device in accordance withcertain operating conditions, and a controlling member common to each ofsaid load reducing mechanisms and adapted to be in one or the other oftwo positions in accordance with which load reducing mechanism isoperative, connections for actuating said common member by one or theother of said load reduction mechanisms, and means whereby when thecommon member is in one position it is adapted to remain thereirrespective of the operation of one of said load reduction mechanisms.

In testimony whereof I atlix my signature. JOHN W. SANFORD.

15. In combination, a power consuming

